Heat sinks comprise extended surfaces that are used to enhance cooling of heat dissipating surfaces. By increasing the overall surface area exposed to a cooling medium (fluid), the rate of heat transfer may be increased. Heat sinks may be fabricated using a variety of materials which employ a number of designs which act to enhance the cooling of the heat dissipating surfaces. Generally, the designs of the heat sinks are intended to decrease the impedance of the fluid flow through the heat sink and, thereby, reduce pressure losses. One commonly used heat sink apparatus is a pin fin heat sink. Pin fin heat sinks are also generally designed to maximize surface area and induce turbulent flow near the pin fins.
A conventional pin fin heat sink apparatus includes a base surface having a plurality of pin fins perpendicular to and protruding from the base surface. The heat sink apparatus is designed so that fluid flows through the plurality of pins which act to enhance the cooling of the heat dissipating surfaces. The plurality of pin fins may be provided in staggered rows on the base surface or the pin fins may be in equally aligned rows on the base surface. Conventional pin fin heat sink apparatuses have used a number of types of pin fins which have a variety of shapes, including, square, triangular, rectangular, diamond, circular, or helical. Typically, a single type of pin fin is used to exchange heat to the cooling medium.
As is known, one of the associated limitations of a heat sink apparatus is that the fluid flow loses a significant amount of its inertial force after entering the heat sink apparatus at one side and the fluid tends to slow as the fluid encounters rows of pin fins and flows toward an opposite side of the heat sulk apparatus. A circular pin fin design which is used in many conventional heat sinks works very well at lower flow rates. However as the flow rate of the system increases, a pressure drop begins to rapidly increase in the heat sink apparatus. Each circular pin fin creates a turbulent wake on the downstream side of the pin at high flow rates contributing to the system pressure drop. In effect, the circular pin fin creates more turbulence than is needed at high flow rates and the turbulence within the heat sink prevents the fluid from effectively flowing through the heat sink increasing the inefficiency of the heat transfer between the pin fin and the cooling medium (fluid). Prior heat fin apparatuses which include an elliptical pin fin design generally do not cause a large drop in pressure; however, the elliptical shape of the pin fin may not cause enough turbulence to provide optimal heat transfer between the pin fin and the cooling medium.
Consequently, there is a need to provide a pin fin arrangement in a heat sink apparatus which offers near optimal heat transfer at high flow rates.